1. Field of Invention
This invention relates to a dressing tool for use in a grinding apparatus provided with a grinding wheel mounted for rotation relative to a stationary base. In particular, the invention relates to a dressing tool adapted to dress the periphery of the grinding wheel to a predetermined radius.
It is often required, for instance in sharpening ice skate runners, to provide a grinding wheel the circumferential portion of which is tangential to the elongation of the runner. Since the elongated runners of skate blades have a concavely curved cross section, it is a requirement that the circumference of the grinding wheel have a correspondingly curved convex cross-section of a required radius.
In another aspect, the requirement may be for grinding with the circumferential surface of a grinding wheel a convexly rounded contour and in such case the grinding surface of the wheel must have a correspondingly concavely rounded contour.
2. Prior Art
A known ice skate sharpening apparatus with a dressing device for providing a desired convex curvature of the circumference of the grinding wheel has been in use in ice skate sharpening shops in North America for some time. It is shown, in a simplified diagrammatic fashion in FIGS. 1 and 2. The two drawings show, respectively, a partial top plan view and a partial side view.
The grinding wheel 1 is driven for rotation in a generally horizontal plane. The grinding device includes a flat, planar base or support table (not shown). Fixedly secured to a stationary cover of the grinding wheel 1 (the cover not shown) is a guide bar 2.
Slidable along the guide bar 2 is a bearing body 3 which is provided with a blocking screw 4. Thus, a selected position of the body 3 along the guide 2 can be fixed. The sliding movement of the body 3 is effected by means of a threaded drive rod 8 provided with a hand knob 9.
An oblique swing arm 11 is secured to the body 3 for swinging about an axis 12. The swinging is effected by manipulating the control knob 13. The end of the arm 11 remote from the body 3 is provided with a laterally angled end portion 14. There is a passage 15 provided in the end portion 14. The passage 15, is provided with a locking screw 5. Slidably received in the passage 15 is a diamond holding rod 6. The rod 6 slides in the direction of the arrow 16 which is parallel with direction 10, to selectively adjust the spacing of the diamond tip 7 from the axis 12. The gauge lines 18 include a centering mark 19. When the centring mark 19 matches the right-hand face of the end portion 14 as shown in FIG. 2, the diamond tip 7 is exactly in line with the pivot axis 12.
Assuming now that the grinding wheel 1 is to be dressed to a convexly shaped radius at its periphery, the size of the radius is determined by the gauge lines 18. The operator simply slides the rod 6 to the appropriate mark to establish the desired radius. If the desired radius is to be convex, the rod 6 and thus the tip 7 is displaced to the right of the position of FIG. 1. If the radius at the periphery of the grinding wheel is to be concave, the displacement of the tip 7 is to the left of the position of FIG. 1. When a proper radius is set, the locking screw 5 is tightened to lock the rod 6.
The hand knob 13 effects the swinging of the arm 11 and thus the end portion 14 about the axis 12, from the position shown in full lines of FIG. 2, to the position 7a which corresponds to the position shown in FIG. 1, and to the opposite side, to the position 7b which is about 180.degree. from the initial position.
This movement causes the diamond tip 7 to circumscribe the desired radius about the axis 12.
With the screw 4 loose, the hand knob 9 is operated to bring the tip 7 to the wheel 1 to enable the dressing of same by swinging about the axis 12. When the dressing is finished, the rod 6 and the diamond is pivoted away from the periphery of the grinding wheel 1.
This known device has several disadvantages. First, since the pivot axis 12 is at an acute angle to the direction 16, the setup of the desired radius at the grinding wheel is relatively complex. Second, two sets of marks are required for proper operation: at the rod 6 and at the hand knob 9. Both marks are exposed to debris generated by the grinding. Thus the adjustment of the desired radius is complex and time consuming.